Although most equipment for playback of sound is two-track stereo, there is a trend toward separately recording several or many tracks, and then subsequently reducing them to two tracks. For example, in recording a piano trio performance, each instrument (e.g., piano, violin, and cello) might be separately recorded through its own microphone.
When two or more audio tracks are recorded, accurate time synchronization among the tracks is essential because the human ear is very sensitive to track misalignment. Consequently, it is convenient to record the multiple tracks onto a single device that guarantees synchronization by handling all tracks uniformly. Each of the three most popular existing technologies—namely, analog multitrack recording to tape; digital multitrack recording to tape; and digital multitrack recording to a computer hard disk—employs this approach.
Such technologies require specialized equipment. In the cases of analog or digital multitrack tape recording, specialized hardware recording equipment is required. Because such specialized equipment has only one use, it is not cost effective for most nonprofessionals to own it. Recording to a computer hard drive requires specialized software. If all tracks are to be recorded at a live event or recording session, each technology requires a separate one-per-track input port or input connection to receive audio information taken from each microphone or other device. The specialized nature and high cost of the three current multitrack recording technologies set a barrier to small groups wanting to produce their own multitrack recordings, especially if synchronized video recording is also to be done. That is unfortunate because new opportunities abound for expression on the Internet through online presentation of audio-visual material.